Work on #403, made example readable and moved methods into utility

promise/etc/promise.ucls

@@ -25,7 +25,7 @@
     <position height="-1" width="-1" x="524" y="313"/>    
     <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
       sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="false" protected="true" private="true" static="true"/>      
+      <attributes public="true" package="false" protected="true" private="false" static="true"/>      
       <operations public="true" package="false" protected="true" private="true" static="true"/>    
     </display>  
   </class>  
@@ -67,42 +67,38 @@
   </interface>  
   <class id="8" language="java" name="com.iluwatar.promise.App" project="promise" 
     file="/promise/src/main/java/com/iluwatar/promise/App.java" binary="false" corner="BOTTOM_RIGHT">    
-    <position height="-1" width="-1" x="992" y="206"/>    
+    <position height="-1" width="-1" x="822" y="251"/>    
     <display autosize="true" stereotype="true" package="true" initial-value="false" signature="true" 
       sort-features="false" accessors="true" visibility="true">      
-      <attributes public="true" package="true" protected="true" private="true" static="true"/>      
+      <attributes public="true" package="true" protected="true" private="false" static="true"/>      
       <operations public="true" package="true" protected="true" private="false" static="true"/>    
     </display>  
   </class>  
-  <generalization id="9">    
+  <realization id="9">    
-    <end type="SOURCE" refId="1"/>    
-    <end type="TARGET" refId="3"/>  
-  </generalization>  
-  <realization id="10">    
     <end type="SOURCE" refId="3"/>    
     <end type="TARGET" refId="2"/>  
   </realization>  
-  <dependency id="11">    
+  <dependency id="10">    
     <end type="SOURCE" refId="1"/>    
     <end type="TARGET" refId="6"/>  
   </dependency>  
+  <dependency id="11">    
+    <end type="SOURCE" refId="1"/>    
+    <end type="TARGET" refId="5"/>  
+  </dependency>  
   <dependency id="12">    
     <end type="SOURCE" refId="8"/>    
     <end type="TARGET" refId="1"/>  
   </dependency>  
   <dependency id="13">    
-    <end type="SOURCE" refId="8"/>    
-    <end type="TARGET" refId="4"/>  
-  </dependency>  
-  <dependency id="14">    
     <end type="SOURCE" refId="1"/>    
     <end type="TARGET" refId="7"/>  
   </dependency>  
-  <dependency id="15">    
+  <generalization id="14">    
     <end type="SOURCE" refId="1"/>    
-    <end type="TARGET" refId="5"/>  
+    <end type="TARGET" refId="3"/>  
-  </dependency>  
+  </generalization>  
-  <dependency id="16">    
+  <dependency id="15">    
     <end type="SOURCE" refId="1"/>    
     <end type="TARGET" refId="4"/>  
   </dependency>  

promise/src/main/java/com/iluwatar/promise/App.java

@@ -21,19 +21,10 @@
  * THE SOFTWARE.
  */
 package com.iluwatar.promise;
-
-import java.io.BufferedReader;
-import java.io.File;
-import java.io.FileReader;
-import java.io.FileWriter;
-import java.io.IOException;
-import java.io.InputStreamReader;
-import java.io.Reader;
-import java.net.URL;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
-import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 
@@ -59,7 +50,12 @@ import java.util.concurrent.Executors;
  */
 public class App {
 
+  private static final String URL = "https://raw.githubusercontent.com/iluwatar/java-design-patterns/Promise/promise/README.md";
+  private ExecutorService executor;
+  private CountDownLatch canStop = new CountDownLatch(2);
+  
   private App() {
+    executor = Executors.newFixedThreadPool(2);
   }
   
   /**
@@ -69,67 +65,80 @@ public class App {
    * @throws ExecutionException if an execution error occurs.
    */
   public static void main(String[] args) throws InterruptedException, ExecutionException {
-    ExecutorService executor = Executors.newSingleThreadExecutor();
+    App app = new App();
     try {
-      promiseUsage(executor);
+      app.run();
     } finally {
+      app.stop();
+    }
+  }
+
+  private void run() throws InterruptedException, ExecutionException {
+    promiseUsage();
+  }
+
+  private void promiseUsage() {
+    
+    countLines()
+      .then(
+          count -> {
+            System.out.println("Line count is: " + count);
+            taskCompleted();
+          }
+      );
+    
+    lowestCharFrequency()
+      .then(
+          charFrequency -> {
+            System.out.println("Char with lowest frequency is: " + charFrequency);
+            taskCompleted();
+          }
+      );
+  }
+
+  private Promise<Character> lowestCharFrequency() {
+    return characterFrequency()
+        .then(
+            charFrequency -> { 
+              return Utility.lowestFrequencyChar(charFrequency).orElse(null); 
+            }
+        );
+  }
+
+  private Promise<Map<Character, Integer>> characterFrequency() {
+    return download(URL)
+      .then(
+          fileLocation -> {
+            return Utility.characterFrequency(fileLocation);
+          }
+      );
+  }
+
+  private Promise<Integer> countLines() {
+    return download(URL)
+        .then(
+            fileLocation -> {
+              return Utility.countLines(fileLocation);
+            }
+        );
+  }
+
+  private Promise<String> download(String urlString) {
+    Promise<String> downloadPromise = new Promise<String>()
+        .fulfillInAsync(
+            () -> {
+              return Utility.downloadFile(urlString);
+            }, executor);
+    
+    return downloadPromise;
+  }
+
+  private void stop() throws InterruptedException {
+    canStop.await();
     executor.shutdownNow();
   }
-  }
   
-  private static void promiseUsage(Executor executor)
+  private void taskCompleted() {
-      throws InterruptedException, ExecutionException {
+    canStop.countDown();
-    String urlString = "https://raw.githubusercontent.com/iluwatar/java-design-patterns/Promise/promise/README.md";
-    Promise<Integer> lineCountPromise = new Promise<String>().fulfillInAsync(() -> {
-      return downloadFile(urlString);
-    }, executor).then(fileLocation -> {
-      return countLines(fileLocation);
-    });
-    
-    Promise<Map<Character, Integer>> charFrequencyPromise = new Promise<String>().fulfillInAsync(() -> {
-      return String.valueOf(downloadFile(urlString));
-    }, executor).then(fileLocation -> {
-      return characterFrequency(fileLocation);
-    });
-    
-    lineCountPromise.get();
-    System.out.println("Line count is: " + lineCountPromise.get());
-    charFrequencyPromise.get();
-    System.out.println("Char frequency is: " + charFrequencyPromise.get());
-  }
-
-  private static Map<Character, Integer> characterFrequency(String fileLocation) {
-    // TODO Auto-generated method stub
-    return null;
-  }
-
-  private static Integer countLines(String fileLocation) {
-    int lineCount = 0;
-    try (Reader reader = new FileReader(fileLocation); 
-        BufferedReader bufferedReader = new BufferedReader(reader);) {
-      for (String line; (line = bufferedReader.readLine()) != null; ) {
-        lineCount++;
-      }
-    } catch (IOException ex) {
-      ex.printStackTrace();
-    }
-    return lineCount;
-  }
-
-  private static String downloadFile(String urlString) throws InterruptedException, IOException {
-    URL url = new URL(urlString);
-    File file = File.createTempFile("promise_pattern", null);
-    try (Reader reader = new InputStreamReader(url.openStream()); 
-        BufferedReader bufferedReader = new BufferedReader(reader);
-        FileWriter writer = new FileWriter(file)) {
-      for (String line; (line = bufferedReader.readLine()) != null; ) {
-        writer.write(line);
-        writer.write("\n");
-      }
-    } catch (IOException ex) {
-      ex.printStackTrace();
-    }
-    System.out.println("File downloaded at: " + file.getAbsolutePath());
-    return file.getAbsolutePath();
   }
 }

promise/src/main/java/com/iluwatar/promise/Utility.java

@@ -0,0 +1,91 @@
+package com.iluwatar.promise;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Map.Entry;
+
+public class Utility {
+
+  public static Map<Character, Integer> characterFrequency(String fileLocation) {
+    Map<Character, Integer> characterToFrequency = new HashMap<>();
+    try (Reader reader = new FileReader(fileLocation); 
+        BufferedReader bufferedReader = new BufferedReader(reader);) {
+      for (String line; (line = bufferedReader.readLine()) != null;) {
+        for (char c : line.toCharArray()) {
+          if (!characterToFrequency.containsKey(c)) {
+            characterToFrequency.put(c, 1);
+          } else {
+            characterToFrequency.put(c, characterToFrequency.get(c) + 1);
+          }
+        }
+      }
+    } catch (IOException ex) {
+      ex.printStackTrace();
+    }
+    return characterToFrequency;
+  }
+  
+  public static Optional<Character> lowestFrequencyChar(Map<Character, Integer> charFrequency) {
+    Optional<Character> lowestFrequencyChar = Optional.empty();
+    if (charFrequency.isEmpty()) {
+      return lowestFrequencyChar;
+    }
+    
+    Iterator<Entry<Character, Integer>> iterator = charFrequency.entrySet().iterator();
+    Entry<Character, Integer> entry = iterator.next();
+    int minFrequency = entry.getValue();
+    lowestFrequencyChar = Optional.of(entry.getKey());
+    
+    while (iterator.hasNext()) {
+      entry = iterator.next();
+      if (entry.getValue() < minFrequency) {
+        minFrequency = entry.getValue();
+        lowestFrequencyChar = Optional.of(entry.getKey());
+      }
+    }
+    
+    return lowestFrequencyChar;
+  }
+  
+  public static Integer countLines(String fileLocation) {
+    int lineCount = 0;
+    try (Reader reader = new FileReader(fileLocation); 
+        BufferedReader bufferedReader = new BufferedReader(reader);) {
+      while (bufferedReader.readLine() != null) {
+        lineCount++;
+      }
+    } catch (IOException ex) {
+      ex.printStackTrace();
+    }
+    return lineCount;
+  }
+
+  public static String downloadFile(String urlString) throws MalformedURLException, IOException {
+    System.out.println("Downloading contents from url: " + urlString);
+    URL url = new URL(urlString);
+    File file = File.createTempFile("promise_pattern", null);
+    try (Reader reader = new InputStreamReader(url.openStream()); 
+        BufferedReader bufferedReader = new BufferedReader(reader);
+        FileWriter writer = new FileWriter(file)) {
+      for (String line; (line = bufferedReader.readLine()) != null; ) {
+        writer.write(line);
+        writer.write("\n");
+      }
+      System.out.println("File downloaded at: " + file.getAbsolutePath());
+      return file.getAbsolutePath();
+    } catch (IOException ex) {
+      throw ex;
+    }
+  }
+}